Appetitive sexual behavior in male rats: 2. sexual reward and level-changing behavior

The immunodeficiency of patients with chronic renal failure (CRF) is related to multiple and complex alterations of the cytokine network and of its target cells such as T or B lymphocytes, monocytes, fibroblasts or endothelial cells. Chronic activation of monocytic functions is recognized as a key factor in these immunological disorders. Since macrophage colony stimulating factor (M-CSF) is essential for the activation of several functions of monocytes and macrophages and their production of cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor alpha, we investigated its involvement in patients with CRF. When measured by ELISA, M-CSF serum levels were significantly higher in patients with progressive CRF and those on hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) than in controls. M-CSF serum levels did not correlate with the degree of renal insufficiency and were probably related to complex alterations in its production and/or degradation by the specific M-CSF receptors of macrophages. In HD patients the M-CSF serum concentrations inversely correlated with the number of circulating lymphocytes and were significantly higher in anemic patients requiring treatment with erythropoietin. Our results suggest that M-CSF may play a role in altering the immune system in uremic patients by maintaining in the circulation and tissues permanently primed monocytes and/or macrophages that can then be triggered to an activated state by secondary stimuli such as endotoxins, complement components, other cytokines or contact with foreign surfaces.     

Decline of sexual behavior in castrated male rats: effects of female precopulatory behavior

Ventricle cells from neonatal rats were cultured in a medium preventing cell proliferation on a modified Roller apparatus with a defined pericellular oxygen partial pressure (pO2) of 38 or 0.6 mm Hg for about one week. The cells were harvested after the second and eighth day of culture (corresponding to one or seven days of culture under a defined pO2) and prepared for electron microscopy. Electron micrographs of this material were examined by stereologic techniques. The obtained results showed some deviations of mitochondrial fine structure of heart muscle cells depending on oxygen supply. During cultivation with a pO2 of 0.6 mm Hg (hypoxic conditions) we observed a proportional increase in mitochondria without cristae and an increase in size accompanied by a more irregular shape. On the contrary, the mitochondria of cells cultured with a pericellular pO2 of 28 mm Hg, which we consider to be a normoxic condition, did not show any deviation of inner membrane arrangement, but an increase in number and a decrease of size during cultivation was apparent. The mitochondria-myofibrils ratio decreased during cultivation in both conditions of oxygen supply. The ratio between sarcoplasmatic reticulum and myofibrils decreased markedly at a pO2 of 0.6 mm Hg.     

Monoaminergic influences on temporal patterning of sexual behavior in male rats

We evaluated the effects of the serotonin (5-HT) presynaptic uptake blocker fluoxetine (FLX) and the dopamine (DA)/noradrenaline (NE) releaser amantadine (AMA), separately and in combination, on the temporal patterning of male rat sexual behavior. FLX alone increased intermount-bout intervals, time-outs, grooming time, ejaculation latency, number of mounts per mount bout, and number of mount bouts per ejaculation. AMA alone had the opposite effect on these measures. Additionally, AMA, when given in combination with FLX, completely reversed the FLX-induced deficits in copulatory behavior. We interpret our results as suggesting an interaction between 5-HT and catecholamines in the temporal patterning of male rat copulatory behavior.     

Effects of losartan on the sexual behavior of male rats

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.     

Age-related deficits in brain estrogen receptors and sexual behavior of male rats

OBJECTIVES: To compare the ability of a computerized method of sperm morphology with the manually recorded method in predicting in vitro fertilization (IVF) results, to compare results obtained by both methods, and to determine the intraobservation variability. DESIGN, SETTING, PATIENTS: Forty-three stained semen slide preparations from two large level-three academic institutions' reproductive endocrinology units (IVF programs) were blindly evaluated, and the sperm were classified into normal and amorphous forms. RESULTS: Experiment 1: Twenty-one slide preparations from the Tygerberg gamete intrafallopian transfer program were manually evaluated; the fertilization rates for the groups with < 14% and > 14% normal sperm forms were 33.3% (15/45 oocytes) and 76.6% (46/60 oocytes), respectively. Corresponding fertilization rates with FERTECH were 46.8% (30/64) and 75.6% (31/41). Experiment 2: Twenty-two slide preparations from the Norfolk IVF program were evaluated. The manual method reported a fertilization rate in the group with < 14% normal forms of 27.4% (14/51 oocytes) compared with 90.0% (127/141 oocytes) in the group with > 14% normal forms. Corresponding figures for the FERTECH method were 33.9% (18/53) and 88.4% (123/139), respectively. Experiment 3: When the 43 slide preparations were blindly evaluated using both methods, 84% of the FERTECH evaluations correlated well with the manual method and FERTECH ability to diagnose the subfertile male (< 14% normal forms) was 95% (sensitivity). Experiment 4: A total of 16 different slides (8 per group) were randomly selected and analyzed five times (100 cells per reading) by the computerized method. The slides were obtained from men with normal sperm morphology of < 14% and > 14% as classified by the manual method. In the first group (< 14%) 97.5% (39/40) of the readings classified the sperm in the proper category, whereas in the second group (> 14%) 95% (38/40) of the cases were correctly identified. CONCLUSION: Using strict criteria for morphology evaluation, there is a positive and significant correlation between FERTECH evaluation and manual assessment. The reproducibility of the computerized method and the ability to distinguish between fertile and subfertile groups using those criteria are good.     

Central progesterone induces female sexual behavior in estrogen-primed intact male rats.

Injection of progesterone induced high levels of female lordotic behavior in 10 of 47 intact, estrogen-primed male Sprague-Dawley rats when it was applied directly to the medial preoptic/anterior hypothalamic area. All 17 Ss previously had shown lordosis when the serotonergic antagonist methysergide was applied to the same central sites. Few Ss responded to systematic progesterone and none to intracranial cholesterol. Intradiencephalic Metycaine, a local anesthetic, induced lordosis in 8 Ss that previously had responded to central progesterone. These data indicate that estrogen and progesterone act synergistically to induce lordosis in male rats when progesterone is administered directly to sensitive brain sites. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Vaginal stimulation in rats induces prolonged lordosis responsiveness and sexual receptivity.

Conducted 2 experiments, using a total of 131 female Sprague-Dawley rats. Sexual receptivity to males resulted from stimulation of the vagina with a glass rod in previously unreceptive ovariectomized, estrogen-treated Ss. Several minutes of rejection behavior preceded the receptivity. In Exp II manual palpation was used to determine the duration of the lordosis response facilitation. Initially, all Ss were unresponsive to manual flank-perineum stimulation (palpation). Vaginal stimulation plus palpation, which together elicited lordosis, facilitated subsequent lordosis responses to palpation. This effect persisted for several hours after the vaginal stimulation was applied. Vaginal stimulation alone, which was ineffective in eliciting lordosis, also facilitated lordosis in response to subsequent palpation. Repeated palpation did not facilitate lordosis. These prolonged effects were independent of hormone treatment. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Opioids and sexual behavior of male rats: Involvement of the medial preoptic area.

Local infusion of β-endorphin (β-END) into the medial preoptic area (MPOA) dose-dependently impaired the gating of the copulatory response and the execution of the sexual performance of sexually experienced, intact male rats. Local naloxone treatment prevented the impairment of the sexual response by β-END, but failed to facilitate unimpaired copulation. Local infusion into the MPOA of equimolar doses of α-endorphin, dynorphin-A-(1-17) or met-enkephalin were less effective than β-END. It is suggested that endogenous opioid systems in the MPOA are normally quiescent, and increased activity may be related to disrupted or inhibited male sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attitude–behavior consistency: An individual difference perspective.

Tested the prediction that only individuals whose past behaviors have been relatively invariant (low behavioral variability) and who tend to infer their attitudes from those past behaviors (low self-monitoring) would express attitudes that summarize past behaviors and, hence, strongly predict future behaviors. In the 1st session, 103 undergraduates completed a self-monitoring scale. Ss' attitudes toward religion were also assessed, and they were asked to indicate the extent to which they varied from one situation to another in how religious they were. In the 2nd session approximately 1 mo later, several measures of Ss' reports of religious behaviors since the 1st session were obtained. Attitude–behavior correlations were then computed within each of the 4 groups of Ss produced by a Low/High Self-Monitoring by Low/High Variability classification scheme. As predicted, only low self-monitors whose past religious behaviors had been relatively invariant manifested high attitude–behavior correlations across all behavioral measures. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of diabetes on sexual behavior and reproductive tract function in male rats

As part of a study of the diversity of myosins, we have cloned a cDNA encoding a myosin-like protein from Arabidopsis thaliana. This is the first molecular motor of any kind to be cloned from a higher plant. The predicted polypeptide (molecular weight 131 kDa) has a motor domain (head) very similar to those of other myosins, but the remainder of the sequence is unusual. The tail contains four potential calmodulin binding sites ("IQ-motifs"), but no sequence motifs suggestive of actin or phospholipid binding, like those found in other myosins. There is also a small region of probable alpha-helical coiled-coil, which suggests that the molecule could be dimeric, though unlikely to form filaments. The N-terminal and C-terminal regions of the molecule are unique. We present a phylogenetic analysis of myosin head sequences, which suggests that this is a new type of myosin.     

Organization of partner preference and sexual behavior and its nocturnal rhythmicity in male rats.

Male rats were neonatally treated with 1,4,6-androstatriene-3,17-dione (ATD), which blocks aromatization of testosterone (T) to estradiol (E?), from Days 0, 2, or 5 through 14. Adult partner preference behavior (PPB; choice between estrous female rat [F] and active male rat [M]) was studied in the early part of the dark phase of the light-dark cycle. ATD Day 0 Ms showed a preference for the stimulus M or showed no preference for either of the stimulus Ss. Controls preferred the estrous F. ATD Days 2 and 5 Ms showed PPB intermediate between ATD Day 0 Ms and controls. Thus the neonatally sensitive period for organization of adult PPB extends beyond Day 5. Furthermore, PPB showed a nocturnal rhythmicity in ATD Ms but not in controls. In the late part of the dark phase, all Ms showed a preference for the stimulus F. ATD Days 2 and 5 Ms and control Ms were no longer different in PPB, but ATD Day 0 Ms still showed significantly lower preference scores for F than all other Ms. Thus the E? metabolite of T suppresses organization of an adult nocturnal rhythm in PPB. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activation of POMC neurons during general arousal but not sexual behavior in male rats.

Exogenous opioids influence male rat sexual behavior, suggesting that endogenous opioid peptides are released during mating. Supporting this hypothesis, the authors recently showed that mating induced activation of mu opioid receptors. However, it is unknown which ligand(s) is acting on these receptors during mating. The current set of experiments tested the hypothesis that beta-endorphin-producing neurons, that is, proopiomelanocortin (POMC) neurons, are activated during sexual behavior. Mating-induced activation of POMC neurons was investigated during either the dark phase or the light phase, following different components of male rat sexual behavior or following control manipulations that resulted in general arousal. Results show activation of POMC neurons in the mediobasal hypothalamus following general arousal but not specifically related to sexual behavior per se. In addition, mating did not activate the subpopulation of POMC neurons that project to the medial preoptic nucleus. These results suggest that it is unlikely that POMC neurons contribute to the action of endogenous opioids in the brain area during sexual behavior but instead may contribute to the change in arousal state essential for the expression of sexual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pain sensitivity and individual differences in self-reported sexual behavior.

The relationship between sexual behavior and pain sensitivity was assessed in 27 heterosexual men and 20 heterosexual women. Sexual behavior measures included sexual motivation and ratings of subjective sexual arousal to and enjoyment of an auditory stimulus. Pain sensitivity measures were pain threshold and pain tolerance in a cold pressor task. Participants were tested after exposure to a neutral or a sexual audio stimulus. Exposure to the sexual stimulus increased pain sensitivity in women but not in men. However, sexual behavior measures were correlated with pain threshold for both men and women. Specifically, higher pain thresholds were associated with weaker sexual motivation, lower enjoyment potential for sexual interaction, and increased inhibition during intercourse. These results are consistent with findings in laboratory animals, suggesting that differences in sexual behavior may reflect differences in responsiveness to a variety of stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypophysectomy facilitates sexual behavior in female rats

Lordosis was elecited in 49% of 87 hormonally untreated, hypophysectomized-ovariectomized (hypox-ovx) female rats in response to palpation of the flanks and perineum (vaginal stimulation was not applied). By contrast, only 12% of 113 hormonally untreated ovariectomized (ovx) rats showed lordosis in response to such stimulation. Subsequently, hypox-ovx and ovx-only rats were given daily injections of 1 mug/kg estradiol benzoate (EB) and tested for sexual receptivity with males. Teh estrogen-treated hypox-ovx females became sexually receptive significantly earlier, and exhibited higher lordosis quotients and more soliciting behavior, than the estrogen-treated ovx-only rats. The increased sexual responsiveness in the hypox-ovx rats could be due to increased LRH activity. To test this, we treated hypox-ovx rats with dihydrotestosterone propionate (DHT-P), which suppresses plasma LH levels but is relatively ineffective in inducing sexual receptivity, and found a significant depression of lordosis responsiveness. These experiments suggest that hypox-ovx females show a heightened responsiveness to hormonal and/or sensory factors that induce a lordosis response, possibly because of increased LRH activity.     

Isolation-induced facilitation of male sexual behavior in mice.

Compared sexual performance of 288 CD-1 male mice housed individually or in groups of 3 or 12. Exp I examined males presented at weekly intervals with ovariectomized, estrogen-primed, progesterone-treated females. Performance in isolates was consistently superior and reached an asymptote that was twice that of grouped Ss. Reversal of housing conditions reversed performance. Exp II varied intervals of isolation among Ss finding facilitation at several intervals. Exp III compared Ss under different population densities. Density did not alter the effects of isolation and grouping. In all experiments, additional tests with target males indicated that aggressive and sexual performances were moderately correlated and responded similarly to parametric manipulations. These results parallel and extend studies of isolation-induced aggression. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal stress and prepuberal social rearing conditions interact to determine sexual behavior in male rats.

The possible interaction between relative amounts of androgen present during specific stages of development and adequate prepuberal social stimulation was evaluated by characterizing the ejaculatory and lordotic behavior potentials of 20 prenatally stressed and 23 control male Sprague-Dawley rats that had been weaned at 16 days of age and raised either in total social isolation or with a same-age female, a control male, or a prenatally stressed male. The decrement in male sexual behavior produced by prenatal stress was attenuated by raising the male with either a female or a control male. Social isolation alone or in combination with stress resulted in severely deficient male behavior. Peripheral skin shock promoted ejaculatory behavior in many previously noncopulating, prenatally stressed males raised with other stressed males, but it was ineffective in most isolated Ss. The high lordosis potential characteristic of prenatally stressed male rats was slightly lower in the group with a female cagemate and was markedly decreased by social isolation. Results support and extend the finding by J. L. Dunlap et al (see record 1980-11465-001) that prenatal hormonal events and prepuberal rearing conditions can interact to attenuate or accentuate the effects that either treatment alone has on the development of adult sexual behavior potentials. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endogenous reproductive hormones and nocturnal rhythms in partner preference and sexual behavior of ATD-treated male rats

Male rats received subcutaneously silastic capsules, containing the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD), shortly after birth. Control males were given silastic capsules containing cholesterol. The capsules were removed at the age of 21 days. In adulthood, blood serum was collected early and late in the dark phase of the light/dark cycle (experiment I). Testosterone and luteinizing hormone and follicle stimulating hormone (FSH) fluctuated nocturnally, both in ATD and control males, with highest levels late in the dark phase. FSH levels were significantly higher in ATD males. Nocturnal levels of inhibin, a selective suppressor of pituitary FSH secretion, also fluctuated in both ATD and control males, with lowest levels late in the dark phase. In experiment II, ATD and control males were tested for partner preference behavior in a three-compartment box (choice: sexually active male vs. estrous female) early and late in the dark phase. When gonadally intact, ATD males, but not controls, showed a clear nocturnal rhythmicity in partner preference behavior and sexual behavior. Early in the dark phase, such ATD males preferred the vicinity of and interaction with a sexually active male. Late in the dark phase, this preference for the active male shifted to a preference for the estrous female. Control males preferred the estrous female. After castration and subsequent treatment with testosterone via silastic capsules, which ensured constant blood serum levels, ATD males continued to show their nocturnal rhythms in partner preference behavior and in sexual behavior. Thus, the underlying mechanism of the nocturnal rhythmicity phenomenon is an organizational effect of neonatal ATD treatment rather than an activational effect of fluctuating serum hormone levels.     

Age-dependent variations in the sexual preference of male rats

Male rats were tested for their sexual preference behavior at either 37, 70, 90, or 150 days of age on three different occasions; while still sexually naive, after sexual experience with a receptive female, and while sexually aroused by having initiated copulation. These tests resulted in the following findings: a) 37-day-old sexually naive males showed a preference for other males and failed to show a preference for either sex after exposure to females; b) 70- and 90-day-old males showed a statistically significant preference for the female after acquiring sexual experience; c) 150-day-old animals showed a female-oriented preference only after being sexually aroused with two intromissions preceding the preference test, and d) none of the age groups tested showed a female-oriented preference without previous exposure to females. It was then concluded that a) female-oriented behavior requires sexual experience and b) the effects of experience varies with age.